code: def test_str_wrong(process_test_df):
      """Test that an invalid Pandas string method raises an exception."""
      with pytest.raises(KeyError):
          process_test_df.process_text(
              column_name="text", string_function="invalid_function"
          )
  
imports: import numpy
  import pandas
  import pytest
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 18 for calling a global function with example usage: test_str_wrong(process_test_df) without return types